Photo Credit: 
Randy Mitchell | For The Chronicle

Well, I promised a column about monarch butterflies, and here it is.

It's not easy, as the subject of monarchs is quite complex. Entomologists know much more about the species now than they did 30 years ago.

These butterflies migrate back and forth from a northern range to a southern range and are the only butterfly in the world that travels such a great distance. However, there is a lot more to it than that.

These butterflies have many generations each year, and the butterflies that migrate south in the fall are not those that flew north in the previous spring. They are the offspring of those monarchs.

Many monarchs migrate through Oklahoma in both the spring and fall. Are monarchs found in Oklahoma year-round? The answer is yes, and no.

 

Oklahoma monarchs

Typically, the monarchs produced in Oklahoma are part of a spring population. However, I have seen these butterflies and their caterpillars in every month of summer, which left me a bit confused.

So, I asked an expert.

I emailed Dr. Kristen Baum. Baum is a professor of integrative biology, CAS co-director for OSUTeach, and associate dean for research. She earned a B.S. in environmental science from the College of William and Mary; an M.S. in wildlife and fisheries sciences from Texas A&M University; and a Ph.D. in entomology from Texas A&M University.

I told her that I wasn't entirely certain of the population in Oklahoma, that I used to be under the impression that monarchs migrate through the state in spring and fall, and that there is a certain period during the summer in Oklahoma when the butterflies are no longer here.

I told her that, since my younger days, I had seen full grown monarch butterflies and caterpillars throughout the summers in years past, but not always.

I sent the email on Aug. 19, saying I had seen two male butterflies the week previous, and someone recently photographed a chrysalis in Oklahoma.

"There have been monarchs around this summer," Baum replied. "After the spring migration, we usually see monarchs (adults and immatures) again starting in mid-August, and then the fall migration coming through in late September through early to mid-October. However, they are around sometimes during the summer, depending on the year. "

So, there you have it. Sometimes they are here during the summer. I knew I wasn't crazy!

 

The migration ... and confusion

The monarch butterflies that spend the summer in the United States east of the Continental Divide in the Rocky Mountains migrate to an area in southern Mexico.

The population which summers west of the divide spends the winter along coast of California, specifically, the southern two-thirds of the state.

There is also a population that winters in southern Florida.

Unless otherwise noted, for the rest of this column, I will be referring to the population which migrates through Oklahoma.

 

The greatest generation

While some generations of monarch butterflies live barely a month, one generation each year lives quite a long time, gets to travel, and even winters in fabulous warm areas. Actually, the places need to be cool for survival. More on that later.

I'll start with that generation, often called the super generation.

These are the butterflies which begin the fall migration, usually around mid-August. The super generation monarchs are bigger, stronger and able to fly much greater distances than the summer generations. Their ability to reproduce is also on hold until the winter is over.

For the eastern population which migrates through Oklahoma, the highest summer monarch reproduction occurs in the "Corn Belt." The area covers only a portion of northeastern Oklahoma, but much of Kansas, Nebraska, the eastern halves of the Dakota states, Minnesota, Iowa, Missouri, Illinois, Indiana and Ohio, etc. Pretty much where large corn crops are produced, that is where monarch production is highest, according to MonarchWatch.org.

However, the summer reproduction occurs over much of the northern half of the United States east of the Rockies. And a little way into Canada, eh, where the northern range of the milkweed plant ends.

The relationship between monarchs and milkweed is one of immense importance, but more on that later.

 

The return home

According to the National Aeronautics and Space Administration, (yes, that NASA) monarchs overwinter in the Transvolcanic Mountains of central Mexico. They gather by the millions atop just 10 to 12 volcanic summits.

The butterflies cling to the trunks, branches and needles of the oyamel fir trees, which only grow on the high slopes of certain mountains in central Mexico.

The climate where monarchs overwinter is just right — not too warm, and not too cold.

The monarchs which traveled to Mexico in autumn leave their roosts about the second week of March. They fly north and east, laying their eggs on milkweed plants as they locate them along the way.

The migrating females that lay the eggs recolonize the southern United States before they die, according to MonarchWatch.org.

The first spring caterpillars hatch and eventually become beautiful orange butterflies.

MonarchWatch.org reports that, over the summer, there are three or four generations of monarch butterflies, depending on the length of the growing season.

Because each female lays hundreds of eggs, the total number of butterflies increases throughout the summer. Before the summer ends, there are once again millions of monarchs all over the U.S. and southern Canada.

 

The milkweed connection

Milkweed is the sole host plant of the monarch butterfly. Females lay eggs on milkweed, and milkweed only, then, upon hatching, the caterpillars eat the leaves of the plants.

Monarch butterflies drink flower nectar.

The leaves of milkweed contain compounds which negatively affects the heart, if ingested. Once the caterpillars — which are immune to the plants effects — eat the leaves, the larvae become toxic and predators typically avoid them.

The population of monarch butterflies has been drastically reduced in the past 20 years, due in large part to the decline of milkweed. Experts believe the use of herbicides, land development and drought are thought to be major causes.

 

Odds and ends

• The monarch butterfly's Mexican wintering site wasn't located by scientists until 1975. Until then, the winter hideouts had been a secret, known only to local villagers and landowners.

• As I mentioned in last week's column, Hackberry Flat Wildlife Management Area near Frederick is a great place to see these butterflies during fall migration. The area's "Monarch Butterfly Watch," a free series of events, takes place this year from Oct. 2-9. Organizers ask that those interested in attending check the status of monarch migration prior to attending by visiting "Friends of Hackberry Flat" on Facebook. In fact, it would be a good idea to like FHF on Facebook anyway.

 

Randy Mitchell is a freelance writer and photographer. He has been an avid birdwatcher, nature enthusiast and photographer for more than 40 years. Reach him at rnw@usa.com.